libc: Add execv()

apps/init.c

@@ -38,5 +38,5 @@ int main()
     fprintf(stderr, "init is running as PID %d\n", getpid());
 
     char* argv[] = { "/bin/hello", "--help", NULL };
-    syscall(SYS_exec, "/bin/hello", argv);
+    execv("/bin/hello", argv);
 }

libc/include/unistd.h

@@ -23,7 +23,9 @@ extern "C"
     /* Return the current process' process ID. */
     pid_t getpid(void);
 
-    int execv(const char*, char* const*);
+    /* Replace the current process with another one. On success, does not return. */
+    int execv(const char* path, char* const* argv);
+
     int execve(const char*, char* const*, char* const*);
     int execvp(const char*, char* const*);
 

libc/src/unistd.cpp

@@ -13,6 +13,12 @@ extern "C"
         return (pid_t)syscall(SYS_getpid);
     }
 
+    int execv(const char* path, char* const* argv)
+    {
+        long rc = syscall(SYS_exec, path, argv);
+        __errno_return(rc, int);
+    }
+
     long syscall(long num, ...)
     {
         va_list ap;